GB849005A - Improvements relating to apparatus for supplying a direct current load from an alternating current source - Google Patents

Abstract

849,005. Control of several D.C. motors. ENGLISH ELECTRIC CO. Ltd. Sept. 11, 1957 [June 13, 1956], No. 18227/56. Class 38 (3). [Also in Group XXXV] Two D.C. traction-motors M1, M2 are energized from an A.C. supply-line 12 through a transformer 11 having two secondary windings 14, 15 with on-load tap-changing arrangements (not shown) and bridge-connected rectifiers R1 R2, R3, R4. In series with each rectifier is one of inductors A1, A2, A3, A4 which steepens its voltage / current characteristic. At a preselected point in the tap-changing sequence when the output D.C. and motor speed are being increased, switches C1, C2 are closed so that the inductors are connected in parallel pairs A1, A2 and A3, A4 in the load circuit in series with motors M1, M2 where they serve only to smooth the D.C. An immediate increase in load voltage results to create in effect a further operating notch. Smoothing chokes B1, B2 may be provided permanently in series with the motors. Connection 16 carries current when there is wheel slip. By reversing rectifiers R2, R4 the rectifiers are arranged in two bi-phased circuits. In modifications, the four inductors are connected between the motors and transformer windings 14, 15 and wound in pairs on two cores, Fig. 2, not shown; the smoothing chokes may each be in two parts each part being on a seperate core with one of the pair of inductors, Fig. 3 not shown; several pairs of motors with their seperate bridge rectifiers may have common inductors and chokes, Fig. 2, 4, not shown.